Controller AC generator for vehicle

ABSTRACT

A vehicle AC-generator controller includes a storage battery to be charged by a rectification output of an AC generator having a field coil, a voltage regulator for controlling an output voltage of the AC generator to a predetermined value by controlling a field current flowing through the field coil, an indicator lamp for indicating a power-generation state and a no-power generation state of the AC generator, an indicator-lamp driving element for turning on and off the indicator lamp, a power-supply driving element for driving power supply of the voltage regulator in accordance with a turn-on-lamp output of the indicator-lamp driving element, and a power-supply cutoff element for cutting off the power-supply driving apparatus by controlling the turn-on-lamp output to the ground potential when the AC generator is brought into the no-power-generation state.

TECHNICAL FIELD

The present invention relates to a vehicle AC-generator controller forestablishing a no-power-generation state in which no power is generatedby cutting off the field current of a vehicle AC-generator when thevehicle AC-generator is brought into the no-power-generation state inorder to reduce the load of an engine, for example, upon start of theengine.

BACKGROUND ART

FIG. 3 is a block diagram of a conventional vehicle AC-generatorcontroller disclosed in, for example, Japanese Patent Publication No.3-47058. In FIG. 3, an AC generator 1 includes a rotor winding 102 andthree three-phase stator windings 101R to 101T connected with each otherin a star-like manner. Diode bridges comprising a full-wave rectifier 2are provided for each phase of the three stator windings 101R to 101T.Voltages induced in the stator windings 101R to 101T by the rotorwinding 102 are full-wave rectified by the full-wave rectifier 2 andapplied to a charge terminal B of a battery 8 through an output terminal201.

An output voltage of the AC generator 1 is adjusted by a voltageregulator 3 in accordance with a charge voltage detected by the chargeterminal B of the battery 8. A source voltage is supplied to the voltageregulator 3 by the battery 8 through an externally provided engine key 7and transistor 5.

The voltage regulator 3 includes a control monolithic IC 303 fordetecting a charge voltage through the charge terminal B of the battery8 to output a field-current control signal having a predetermined dutyratio corresponding to the level of the charge voltage as well as fordetecting a no-power-generation state of the AC generator 1 inaccordance with an induced voltage applied to the stator winding 101S tooutput a no-power-generation detection signal, a power transistor 306having a base adapted to be inputted by a field-current control signal,a grounded emitter and a collector connected to the positive side of thebattery 8 through a reversely connected diode, and a power transistor301 having a base adapted to be inputted by a no-power-generationdetection signal, a grounded emitter and a collector connected to an endof a charge lamp 6.

Moreover, when the power transistor 306 is turned on, a field currentflows through the rotor winding 102, power transistor 306 and groundfrom the battery 8. Moreover, when the power transistor 301 is turnedon, a current flows from the battery 8 to ground through the engine key7, charge lamp 6 and power transistor 301 to turn on the charge lamp 6.Resistances 302 and 304 for applying a base voltage to the powertransistors 301 and 306 are connected between the bases of the powertransistors 301 and 306 and the power-supply line of the controlmonolithic IC 303.

A transistor 301 constituting an external unit 4 is connected at itscollector to the base of the transistor 5 for supplying a source voltageto the control monolithic IC 303 through a resistance 402. An emitter ofthe transistor 301 is grounded and a signal indicative of the drivingstate of a vehicle (a driving-state signal) is input to the base of thetransistor 301 from various sensors and switches (not shown).

In this case, the operation-state signal denotes a signal such as anon-output signal of an unillustrated starter switch or anengine-cooling-water-temperature signal of an unillustrated watertemperature sensor. The external unit 4 inputs an off signal to thetransistor 301 for a certain period of time in accordance with eachsignal in order to reduce the load of an engine when the engine isstarted. As a result, the transistor 5 is turned off, thereby cuttingoff the supply of power from the battery 8 to the control monolithic IC303 and stopping the generation of a field current.

In the operation of a conventional controller, when the controlmonolithic IC 303 detects a voltage drop of the battery 8 after anengine is started, it turns on and off the power transistor 306 at apredetermined duty ratio to intermittently supply a field current to therotor winding 102 from the battery 8. By supplying the field current, aninduced voltage is generated in the stator windings 101R to lost by amagnetic field generated in the rotor winding 102. Moreover, thegenerated induced voltage is full-wave rectified by the full-waverectifier 2, applied to the charge terminal B through the outputterminal 201, and charged to the battery 8.

Moreover, when the control monolithic IC 303 detects a voltage drop ofthe battery 8 immediately after the engine key 7 has been turned on(i.e., immediately after the engine has been started), the monolithic IC303 turns on the power transistor 306 to supply a field current to therotor winding 102 from the battery 8 to thereby form a magnetic field inthe AC generator 1. In this case, however, because the engine is notoperated to run, the AC generator 1 does not generate power, resultingin the no-power-generation state.

When the control monolithic IC 303 detects the no-power-generation statefrom the stator winding 101S, it drives the power transistor 301 to turnon the charge lamp 6, thus notifying the driver that the battery 8 iscurrently discharging.

However, when the AC generator 1 starts the power-generating operationby forming a magnetic field in the generator 1 immediately after anengine has started, particularly during a cold period when the functionof a battery is deteriorated, the engine rotation becomes unstable dueto fluctuation of the generator load torque. Therefore, immediatelyafter start of the engine, the transistor 5 is turned off upon anoperation-state signal being inputted to the transistor 301 in the formof the external unit 4 for a certain time until the speed of the enginereaches a predetermined value, thereby turning off the transistor 301 tocut off the supply of power to the control monolithic IC 303. Becausethe supply of power is cut off, the control monolithic IC 303 stopsgenerating an output to the power transistor 306 to thereby cut off thefield current, and hence the AC generator 1 is forced into theno-power-generation state.

Thus, because the source voltage of the control monolithic IC 303 is cutoff, no field current is supplied to the rotor winding 102 and the ACgenerator 1 is brought into the no-power-generation state. However, whenthe above configuration is used, the transistor 5 having a large currentcapacity for cutting off a power supply is necessary in addition to theexternal unit 4 and thus, a large-scale circuit configuration isrequired.

Moreover, if, for any reason, a leak current is supplied to thepower-supply terminal of the control monolithic IC 303 due to a positivepotential, a problem occurs in that the power supply cannot be cut offby the external unit 4 and thus, the no-power-generation state cannot berealized.

The present invention is intended to solve the above problems and itsobject is to provide a vehicle AC-generator controller capable ofbringing an AC generator into a no-power-generation state by cutting offa field current in order to reduce the load of an engine upon startingthereof.

DISCLOSURE OF THE INVENTION

The present invention according to one aspect includes a vehicleAC-generator controller includes a storage battery to be charged by arectification output of an AC generator having a field coil, a voltageregulator for controlling an output voltage of the AC generator to apredetermined value by controlling a field current flowing through thefield coil, detection means for detecting a power-generation state and ano-power-generation state of the AC generator, an indicator lamp forindicating the power-generation state and the no-power-generation stateof the AC generator, indicator-lamp driving means for turning on and offthe indicator lamp in accordance with the detection result of thedetection means, power-supply driving means for driving a power-supplycircuit of the voltage regulator in accordance a turn-on-lamp output ofthe indicator-lamp driving means, and power-supply cutoff means forcutting off the power-supply driving means by controlling theturn-on-lamp output to a ground potential when the AC generator isbrought into the no-power-generation state.

Upon start of an internal combustion engine of a vehicle, thepower-supply cutoff means of the present invention controls theturn-on-lamp output to the ground potential for a certain time tothereby cut off the power-supply driving means so that the AC generatoris thereby brought into the no-power-generation state.

The present invention according to another aspect includes a storagebattery to be charged by a rectification output of an AC generatorhaving a field coil, switching means to be turned on and off at apredetermined ratio to intermittently supply a field current to thefield coil, a voltage regulator for controlling an output voltage of theAC generator to a predetermined value by inputting a control signal forcontrolling an on/off ratio of the switching means, and field-currentcutoff means for cutting off a field current by controlling a signalinput section of the switching means to a ground potential when the ACgenerator is brought into a no-power-generation state.

Upon start of an internal combustion engine of a vehicle, thefield-current cutoff means of the present invention controls the signalinput section of the switching means to the ground potential for apredetermined time to thereby cut off the field current so that the ACgenerator is thereby brought into the no-power-generation state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a vehicle AC-generator controller accordingto embodiment 1 of the present invention;

FIG. 2 is a block diagram of a vehicle AC-generator controller accordingto embodiment 2 of the present invention; and

FIG. 3 is a block diagram of a conventional vehicle AC-generatorcontroller.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in greater detail below withreference to the accompanying drawings.

Embodiment 1

The embodiment 1 of the present invention will be described below withreference to the accompanying drawings. Portions that are the same as orcorrespond to those of a conventional controller have the same referencenumerals. FIG. 1 is a block diagram of a vehicle AC-generator controllerof this embodiment. Compared to the above-described conventionalcontroller, the vehicle AC-generator controller of this embodiment dosenot have the transistor 5 for directly supplying a battery voltage to acontrol monolithic IC 303.

Moreover, a voltage regulator 3A of this embodiment includes atransistor 307 having a grounded emitter and a base connected to acollector of a power transistor 301 for turning on a charge lamp througha resistance 309, and a transistor 308 having an emitter connected to apositive terminal of a battery 8 and a collector connected to a base ofa power transistor 306 for outputting a field current through aresistance 304. Moreover, the transistor 307 has a collector connectedto the base of the transistor 308 through a resistance 310.

Furthermore, the voltage regulator 303 and the stator winding 101Stogether constitute a detection means; the power transistor 301constitutes an indicator-lamp driving means; the transistor 308 and theresistance 309 together constitute a power-supply driving means; and theexternal unit 4A constitutes a power-supply cutoff means.

Next, the operation of this embodiment will be described below. First,when supplying a source voltage to the control monolithic IC 303 fromthe battery 8, by turning on an engine key switch 7, a battery voltageis applied to the base of the transistor 307 through a charge lamp 6 andthe resistance 309. As a result, the transistor 307 is turned on and acurrent flows through a resistance 310, the collector, and the emitterthereof. When the current flows, the transistor 308 is turned on and abattery voltage is applied to the power-supply terminal of the controlmonolithic IC 303 through the emitter and collector of the transistor308.

When the control monolithic IC 303 detects a voltage drop of the battery8 after start of the engine, it turns on the power transistor 306, thuspermitting a field current to intermittently flow from the battery 8 tothe rotor winding 102 to cause the AC generator 1 to generate power.

Moreover, when the control monolithic IC 303 detects based on thevoltage of the stator winding 101S that the power-generation output ofthe AC generator 1 is in the no-power-generation state upon enginestarting, the control monolithic IC 303 drives the power transistor 301to turn on the charge lamp 6 so that the driver is thereby notified ofthe battery 8 being currently discharging.

Next, the operation for bringing the AC generator 1 into theno-power-generation state in order to reduce the load of an engine uponengine starting will be described below. By inputting an operation-statesignal to a transistor 401 constituting an external unit 4A to turn iton when the engine is started, the voltage applied to the charge lamp 6is brought into the ground potential through the transistor 401.

Therefore, the base voltage of the transistor 309 is brought into theground potential so that the transistor 309 is turned off to thereby cutoff the base current of the transistor 308, thus turning it off. Whenthe transistor 308 is turned off, the battery voltage applied to thecontrol monolithic IC 303 is cut off. As a result, a field-currentcontrol signal is not inputted to the power transistor 306 from thecontrol monolithic IC 303 and thus, the transistor 306 is turned off andthe no-power-generation state is attained because a magnetic field isnot generated in the rotor winding 102 by a field current.

As described above, this embodiment makes it possible to inexpensivelyconfigure a controller and reduce its size because it is unnecessary toexternally provide a source-voltage-cutoff transistor other than theexternal unit 4A between the voltage regulator 3A and the outputterminal of the battery 8.

Moreover, because the controller of this embodiment is constructed suchthat a source voltage is not directly supplied to the power-supplyterminal of the control monolithic IC 303 from the battery 8, theproblem is solved wherein a leak current is generated in thepower-supply terminal due to a positive potential which disables thepower-supply cutoff operation so that the no-power-generation statecannot be realized. Thus, it is possible to improve the reliability ofthe controller.

Embodiment 2

In the above-described embodiment 1, the supply of a field current tothe rotor winding 102 is stopped by stopping the operation of thecontrol monolithic IC 303 so that the AC generator 1 is brought into theno-power-generation state. However, in embodiment 2, the operation of acontrol monolithic IC 303 is continued while cutting off only the fieldcurrent which is to be supplied to the rotor winding 102.

FIG. 2 is a block diagram of a vehicle AC-generator controller accordingto this embodiment. In FIG. 2, the same reference numerals as those inFIG. 1 denote the same or corresponding portions. An external controlunit 3B of this embodiment is not connected to one end of the chargelamp 6 but is connected to the base of the field-current output powertransistor 306.

Moreover, the power transistor 306 constitutes a switching means, andthe external unit 4B constitutes a field-current cutoff means.

Therefore, according to the above configuration, in order to bring theAC generator 1 into the no-power-generation state by stopping the fieldcurrent to be supplied to the rotor winding 102 upon start of theengine, the power transistor 306 is turned off by inputting anoperation-state signal to a transistor 301 constituting the externalunit 4B for a certain time to turn on the transistor 301 whereby thebase of the power transistor 306 is set to the ground potential.

As a result, it is possible to cut off the field current to be suppliedto the rotor winding 102, thus bringing the AC generator 1 into theno-power-generation state. In this case, because the control monolithicIC 303 detects the no-power-generation state through the stator winding101S of the AC generator 1, it is operated to supply a base current tothe power transistor 301 to turn it on, so that the charge lamp 6 is litto indicate the no-power-generation state to the operator.

Thus, because this embodiment temporarily stops the field current to besupplied to the rotor winding 102 while maintaining the operating stateof the control monolithic IC 303, in addition to the advantages of theembodiment 1, it is possible to smoothly start the power-generatingoperation of the AC generator 1.

INDUSTRIAL APPLICABILITY

As described above, the present invention is suited to constructing acontroller with a reduced circuit scale and improved reliability, whichserves to forcibly bring an AC generator into a no-power-generationstate in order to reduce the load of an engine upon start thereof.

What is claimed is:
 1. A vehicle AC-generator controller characterizedby: a storage battery to be charged by a rectification output of an ACgenerator having a field coil; a voltage regulator for controlling anoutput voltage of the AC generator to a predetermined value bycontrolling a field current flowing through the field coil; detectionmeans for detecting a power-generation state and a no-power-generationstate of the AC generator; an indicator lamp for indicating thepower-generation state and the no-power-generation state of the ACgenerator; indicator-lamp driving means for turning on and off theindicator lamp in accordance with the detection result of the detectionmeans; power-supply driving means for driving a power-supply circuit ofthe voltage regulator in accordance a turn-on-lamp output of theindicator-lamp driving means; and power-supply cutoff means for cuttingoff the power-supply driving means by controlling the turn-on-lampoutput to a ground potential when the AC generator is brought into theno-power-generation state.
 2. The vehicle AC-generator controlleraccording to claim 1, characterized in that upon start of an internalcombustion engine of a vehicle, the power-supply cutoff means controlsthe turn-on-lamp output to the ground potential for a certain time tothereby cut off the power-supply driving means so that the AC generatoris thereby brought into the no-power-generation state.
 3. A vehicleAC-generator controller characterized by: a storage battery to becharged by a rectification output of an AC generator having a fieldcoil; switching means to be turned on and off at a predetermined ratioto intermittently supply a field current to the field coil; a voltageregulator for controlling an output voltage of the AC generator to apredetermined value by inputting a control signal for controlling anon/off ratio of the switching means; and field-current cutoff means forcutting off a field current by controlling a signal input section of theswitching means to a ground potential when the AC generator is broughtinto a no-power-generation state.
 4. The vehicle AC-generator controlleraccording to claim 3, characterized in that upon start of an internalcombustion engine of a vehicle, the field-current cutoff means controlsthe signal input section of the switching means to the ground potentialfor a predetermined time to thereby cut off the field current so thatthe AC generator is thereby brought into the no-power-generation state.